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Large‐scale manufacturing of perovskite solar cells (PSCs) requires the deposition of homogeneous and defect‐free perovskite films on large‐area substrates. Up to now, the knowledge developed for industrial slot‐die processing has not been fully transferred to the perovskite photovoltaic community. Here, the deposition of uniform perovskite layers by slot‐die coating (SDC). Computer fluid dynamics (CFD) simulations, experimental validation, and calculation of industrial uniformity parameters are demonstrated, which enabled to establish processing conditions for SDC of perovskite ink. This approach allowed for obtaining stable cross‐web flow in the slot‐die head resulting in the formation of a stable coating bead yielding uniform perovskite films. The best processing parameters are used for the fabrication of slot‐die‐coated PSCs, which showed a more homogeneous spatial distribution of photovoltaic parameters compared to their spin‐coated counterparts. Better reproducibility observed in device performance is a step forward toward the commercialization of perovskite photovoltaic technology. For the first time, the industrial approach used for the optimization of slot‐die coating is applied for the processing of perovskite inks that have special conditions such as low viscosity and in situ crystallization on the substrate. [ABSTRACT FROM AUTHOR]

Perovskite solar technology stands on three different pillars: efficiency, stability, and processability. Focusing on processability, the field demands the achievement of optoelectronic grade active layers with high uniformity fabricated by industry‐compatible methods. Herein, the design and implementation of an air knife on a blade coating deposition system, which allows controlling the evaporation rate of the solvents improving the crystallization and uniformity of perovskite films in a p–i–n device are reported. The effect of doctor blade operational parameters is studied using image analysis combined with a machine learning method to identify the most relevant processing variables leading to a uniform perovskite layer with optimal thickness. After implementing the air knife system and finding the best processing conditions, a special perovskite solar minimodule enabling the evaluation of single inner subcells is fabricated. These perovskite subcells reach an average efficiency of 10.1% and remarkably all the subcells deviate less than 20% from this value over a large‐area substrate. These results demonstrate the promising potential of this fabrication method for low cost and high deposition rate photovoltaic devices, which is on the path to mass production. [ABSTRACT FROM AUTHOR]

ABSTRACT: When making nanocomposites, there is a big challenge to obtain both functional and mechanical enhancement. In this study, a new in situ polymerization methodology for the incorporation of surface modified silver nanoparticles (AgNPs) in a thermoplastic polyurethane matrix was developed. AgNPs with contents ranging from 0 to 1.5 wt % were used. A double functionalization of the nanoparticles with oleic acid was performed, which lead to a reaction of carboxylic acid groups in the nanoparticle's surface with isocyanate groups of the 4,4′‐methylene diphenyl diisocyanate monomer as corroborated from the Raman results. The successful incorporation of the nanoparticles was verified with EDS, TGA, and Raman measurements. Thermal properties of nanocomposites were investigated by DSC. AgNPs made positive impact in two ways: first, increased more than twice the elastic modulus, as studied via nanoindentation measurements and second, based on the inhibition zone method, great bactericidal effectiveness for nanocomposites containing 1.5 wt % AgNPs was observed for Escherichia coli. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46180. [ABSTRACT FROM AUTHOR]

This work investigates the two-step polymerization between methylene diphenyl diisocyanate (MDI), two different poly(tetramethylene oxide) macrodiols, and 1,4-butanediol (BD) as chain extender. At the end of the prepolymerization, the reaction mixture contains MDI in excess and a prepolymer with isocyanate end group. Then, BD and a solvent (tetrahydrofuran) were added to start the finishing stage under nominal stoichiometric equilibrium. The reaction was analyzed by Fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance (1H-NMR), and size exclusion chromatography. 1H-NMR was employed to follow global concentrations of unreacted isocyanate end groups and internal urethane groups. This information enabled to estimate the following "effective" rate constants: k1 =1.07 x 10-3 L mol-1 s-1 for the prepolymerization; and k2=1.94 x 10-4 L mol-1 s-1 for the finishing stage. These values are subject to errors caused by biases introduced in the recipe, in the measurements, in the reaction conditions, in the quality of reagents, and in the reaction mechanism assumptions. Such errors also explain the dispersion of the published rate constants values. The ¹H-NMR measurements also enabled to estimate the evolution (with extent of reaction) of the numberaverage number of structural units along the prepolymerization and finishing stages; and such estimates reasonably verify Flory's classical expressions. [ABSTRACT FROM AUTHOR]

This article presents the variation of viscosity, gel point, and curing kinetic process of nanocomposites based on unsaturated polyester resin (UPR) and natural nano-clay CloisiteNa+® and organomodified Cloisite15A® montmorillonites (MMT). Different amounts (1-10 wt%) of nanoclays were added homogeneously before the cross-linking reaction of the thermoset polymer. The complex viscosity before curing was especially dependent on the CloisiteNa+® content more than Cloisite15A®. The G' and G'' slope also as the complex viscosity criterion were used to determine the nanocomposites gel time variation. Isothermal differential scanning calorimetry measurements were performed to calculate the reaction order and the rate constant using different empirical equations. These results demonstrated a catalytic effect of the clays on the UPR cure, with diffusion controlled phenomena predominating at high conversions. The X-ray diffraction patterns were useful for identifying the nanocomposites formation, and gave information about the clays dispersion, which served to support the rheological and polymerization kinetic results. Finally, natural MMT CloisiteNa+®decreased gel time and was more compatible with UPR than the organomodified Cloisite15A®. POLYM. COMPOS., 36:1931-1940, 2015. © 2014 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

ABSTRACT Novel segmented polyurethane elastomers were successfully synthesized by a nonisocyanate route using dicyclic carbonates as precursors for both soft and hard segments. The hard segment was prepared from the dicyclic carbonate of bisphenol A and m-xylylenediamine as chain extender. The soft segment was poly(tetramethylene ether) glycol of molecular weight 1000. Three polyurethanes with different morphologies were made with soft segment concentration of 70, 50, and 30%. Method of synthesis consisted in preparation of dicyclic carbonate of bisphenol A from a commercial epoxy resin and carbon dioxide, while dicyclic carbonate of poly(tetramethylene ether) glycol (PTMEG) was made from previously prepared diglycidyl ether of PTMEG and carbon dioxide. Polymers were prepared by reacting dicyclic carbonates with m-xylylenediamine by one-pot process. The monomers and polymers were characterized by Fourier transform infrared spectroscopy, differential scanning chromatography, thermogravimetric analysis, 1H NMR, 13C NMR, scanning electron microscopy, and mechanical measurements. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42492. [ABSTRACT FROM AUTHOR]

ABSTRACT Kinetics of curing of maleated castor oil glycerides with styrene was studied by differential scanning calorimetry and rheology. The resin was synthesized from biodiesel-derived crude glycerol. Curing rates were fitted to several empirical models (autocatalytic model, Kamal's model and a model with vitrification). The three models showed a good fitting with experimental data at conversions lower than 0.55 for temperatures ranging from 30 to 50°C. However, the model that includes vitrification showed a better fitting in the entire range of conversions and the same temperatures. At higher temperatures (50-60°C), some deviations were observed for the three models at low and high conversions. Gel times were obtained from rheological studies and the apparent activation energies were calculated thereof. Gel times were 300-2700 s. The values of apparent activation energy obtained for this castor oil-based copolymer (47.2-52.3 kJ/mol) were within range of commercial unsaturated polyester resins. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41344. [ABSTRACT FROM AUTHOR]